WOOD' The term 'TREE YIELD' can be broken down into two crossword solutions, SAP and WOOD. SAP is a three letter word that refers to the sugary liquid that circulates through a tree's vascular system, providing nutrients and energy for growth. WOOD is a four letter word that refers to the hard, fibrous material that makes up the trunk and branches of a tree. Together, these two words represent the yield of a tree, which is the products or materials that are harvested from it.